A lot of attention has been given recently to biodiesel production from all sorts of oil sources. One of the most promising ones is the use of microalgae, whether from marine or fresh water strains. These algae are known to be able to achieve very high productivity and good oil yields if the right conditions are met. A lot of research has been dedicated to try to find the most productive and/or resilient algae streams at universities and research institutes. This part of the field is advancing at a relatively good pace.
The same is not true though to cultivation methods. Mostly the research has been conducted at laboratory scales or small scale pilot projects and the main focus so far has been to verify the yield potential of the most promising streams into crude bioreactors or race ponds.
The main concept behind growing the selected stream is relatively straightforward, all that is needed is a suitable infrastructure capable of holding the necessary amount of water, keep critical culture parameters such as water temperature, PH, nutrient and carbon dioxide (CO2) concentration within acceptable boundaries and prevent contamination of the water culture from other undesirable organisms.
Despite the relatively straight forward requirements, many technical challenges arise when trying to scale up designs that work on table tops or producing new ones that are from the beginning designed as large scale. Particularly challenging is to find ways to keep costs as low as possible without losing the ability to effectively perform all necessary tasks. Those challenges have so far prevented the successful design and deployment of cost effective bioreactors that perform to the required level.
The high capital and operating costs of existing cultivation alternatives have so far prevented the promise of microalgae to be fully fulfilled. The main cost incurring items are the procurement of large cultivation areas close to a source of CO2, the preparation of the terrain and the installation of costly equipment such as the bioreactor structures, pumps, filters, sensors etc. All this equipment needs a lot of energy to operate generating high operating costs that in conjunction with the initial high capital costs create a very demanding productivity threshold to have an economical project.
The operating cost is a big challenge to overcome. So far existing reactor designs require a considerable amount of energy to run, mostly in pumping and controlling water temperature throughout the day and over the year. Most microalgae streams are very sensitive to temperature and PH levels outside their ideal growth range and if the ideal conditions are not met the productivity drops significantly and in some cases the algae die or are harmed and the productivity is irrecoverably reduced.
A lot of research has been dedicated to find better suited streams, more resilient to variations of the water culture and at the same time able to produce high oil yield. Some lines of research have tried to genetically modify high productivity streams to become resilient or high resilient ones to become more productive for oil yield but this created a concern of what could happen if these streams escape into the environment during the large scale phase of the project.
What is needed is an integrated approach that tackles the multiple aspects of the cultivation of microalgae which requires: 1) a system that significantly reduces capital and operational costs and ensures good control of the environment parameters; 2) a system that maintains the ideal conditions for the growth of the selected microalgae stream during all the different phases of the cultivation so productivity can be as high as possible. For any system to be successful, the system needs to be constructed with cheap materials to minimize capital costs, be very simple and robust to reduce maintenance costs, run as much as possible autonomously not requiring constant human intervention and have integrated safety mechanisms to prevent contamination of the culture and the environment in case of failure of the equipment.